Method and apparatus for forming optical elements by inducing changes in the index of refraction by utilizing electron beam radiation

ABSTRACT

The exposure of selected optical materials to large area electron beam irradiation can raise the refractive index of the optical material to allow the fabrication of waveguides, optical fibers, gradient index lenses, interference filters, antireflection coatings, heat reflective thermal control coatings and other optical elements.

This application is a continuation-in-part of U.S. patent applicationSer. No. 10/183,784 titled “Method And Apparatus For Forming OpticalMaterials And Devices” filed on Jun. 27, 2002, now U.S. Pat. No.7,026,634 which claims the benefit of U.S. Provisional Application No.60/302,152 titled “Novel Optical Materials Formed Using Electron BeamIrradiation And Methods For Forming Optical Devices” filed on Jun. 28,2001.

This application is related to co-pending U.S. patent applicationNo./“Optical Elements Formed By Inducing Changes In The Index OfRefraction By Utilizing Electron Beam Radiation”/“Method And ApparatusFor Forming Optical Elements By Inducing Changes In The Index OfRefraction By Utilizing Electron Beam Radiation”/, filed on the samedate as the present application, with the same inventors and commonlyassigned to the same assignee as the present invention and hereinincorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to the optical elements havingat least two optical material layers having different refractive indexesand more specifically to optical elements having at least two layers ofthe same optical material but with different refractive indexes and amethod for fabricating optical elements by inducing changes in the indexof refraction in optical materials utilizing large area electron beamradiation.

Various optical elements have a multiple layer structure of layers ofdifferent optical materials having different indexes of refraction or amultiple layer coating of layers of different optical materials havingdifferent indexes of refraction. These multiple layer optical elementshave a variety of uses in total internal reflection, wavelength filtersand diffraction.

An optical waveguide carries a light beam along a designated path withinthe waveguide. The optical waveguide is typically formed by utilizingmaterials of different refractive index. The inner waveguide is formedof a first optical material having a high index of refraction. The outercladding layer around the inner waveguide is formed of a seconddifferent optical material having a second low index of refraction.

The inner waveguide material typically exhibits high opticaltransmission for a light beam to maximize the internal reflection of alight beam traveling along the inner layer of the waveguide and tominimize the signal loss of the light beam. The current state of the artof producing these waveguides and producing these materials of differentindex of refraction is to utilize two different materials, which arelayered in an additive or subtractive process.

Similarly, the inner cylindrical core layer of an optical fiber willhave a high index of refraction while the surrounding cylindricalcladding layer will have a low index of refraction to maximize theinternal reflection of a light beam traveling along the inner core ofthe optical fiber.

An interference filter is formed by a first layer of high refractiveindex material on a substrate with a second layer of a low refractiveindex material on the first layer. The interference filter can be anantireflection coating to reduce reflected light by decreasing therefractive index difference between the substrate next to the firstlayer and the ambient atmosphere next to the second layer. Theinterference filter can be a heat reflective thermal control film, whichtransmits visible radiation while reflecting infrared radiation. Theinterference filter can also be used to reflect or transmit selectedwavelengths of light or reflect or transmit ranges of wavelengths oflight.

Alternating layers of high and low refractive index materials can beused as diffraction gratings or beamsplitters.

The index of refraction can vary within a layer or across multiplelayers to form gradient index optical elements. Optical waveguides andoptical fibers can have gradient indexes. A gradient index lensfunctions by diffraction from the layers of different refractiveindexes, rather than the traditional refraction from the curved surfaceof a lens made from a single material having a single index ofrefraction.

The two different materials with different indexes of refraction arestructurally and/or chemically distinct and are brought together duringthe assembly process for the optical element.

Typically, these optical elements are fabricated by chemical vapordeposition of the layers of different optical materials. However thislimits the possible optical material layers since the layers must becompatible with fabrication by deposition and affinity for bonding witheach other. Similarly, the optical materials may require differentexposure times, temperatures, pressures and atmospheres which may alterthe other optical material.

In waveguides and optical fibers in particular, an optical adhesive maybe mandated to bond the layers of structurally and chemically distinctmaterials together. The adhesive layer will effect waveguiding inwaveguides and optical fibers and also effect transmittance andreflectance if used in other optical elements.

The multiple layers of different materials create problems infabrication as edge breakage and differential polishing rates betweenthe glue and core/cladding materials must be taken into account as wellas controlling appropriate glue thickness.

Separate from the fabrication issue is that the dissimilar opticalmaterials may have different coefficients of thermal expansion whichwill cause the fabricated optical element to function differently or notat all at different temperatures.

It is an object of the present invention to provide different refractiveindexes from the same optical material within an optical element.

SUMMARY OF THE INVENTION

According to the present invention, the exposure of selected opticalmaterials to large area electron beam irradiation can raise therefractive index of the optical material to allow the fabrication ofwaveguides, optical fibers, gradient index lenses, interference filters,antireflection coatings, heat reflective thermal control coatings andother optical elements.

The selected starting optical material is deposited on a substrate. Theoptical material is then exposed with the electron beam at an energy anddose, while the substrate is heated to the appropriate temperature, toraise the refractive index of the selected optical material on thesubstrate. The optical material and substrate are preferably loaded intoa vacuum chamber with a flood electron source to expose the top side ofthe substrate and a heating element to apply heat to the back-side ofthe substrate. The method utilizes a large area electron beam exposuresystem in a soft vacuum environment. By adjusting the processconditions, such as electron beam total dose and energy, temperature ofthe selected optical material, and ambient atmosphere, the refractiveindex of the optical material can be altered to become either a gradientindex of refraction or a uniform index of refraction.

The electron beam can partially penetrate the single optical materiallayer. A single optical material layer can have a first index ofrefraction. Only the upper portion, or sub-layer, of the single layer isexposed to large beam electron beam radiation. After irradiation, theupper portion of the single layer has a higher index of refraction thanthe lower portion of the layer, also a sub-layer, which still has thefirst original index of refraction. The two sub-layers are integral andadjacent to each other. These alternating sub-layers of high and lowindexes of refraction can be used as interference filters, ananti-reflection coating for an optical element, a heat reflectivethermal control layer for an optical element or a wavelength sensitivereflectance/transmittance interference filter for an optical element.Multiple alternating sub-layers of high and low indexes of refractioncan be used as diffraction gratings or beam-splitters.

The use of an aperture mask or an embossing structure controls andlimits the electron beam exposure to certain specified areas or sectionsof the optical material layer. The optical material layer can have afirst index of refraction. Only the portion of the optical materiallayer exposed through the aperture or embossed structure is exposed tothe large beam electron beam radiation. After irradiation, the exposedareas or sections of the optical material layer have a higher index ofrefraction than the remaining unexposed portion of the optical materiallayer, which still has the first original index of refraction.

High index of refraction areas of the optical material on the low indexof refraction optical material layer can form a microlens array, adiffraction grating or a beam-splitter. The high refraction areas of theoptical material can form the core layer of a waveguide with thepartially or completely surrounding low index of refraction opticalmaterial layer forming the cladding layer of the waveguide.

Alternating sections of optical material of high and low indexes ofrefraction can be used as diffraction gratings or beam-splitters. Layersof optical material of high index of refraction within the opticalmaterial layer of low index of refraction can form a binary diffractiveoptical element.

The electron beam apparatus and method can form an optical fiber for useas a waveguide having a core of a high refractive index surrounded by acladding layer of a low refractive index formed of the same opticalmaterial.

The foregoing has outlined, rather broadly, the preferred feature of thepresent invention so that those skilled in the art may better understandthe detailed description of the invention that follows. Additionalfeatures of the invention will be described hereinafter that form thesubject of the claims of the invention. Those skilled in the art shouldappreciate that they can readily use the disclosed conception andspecific embodiment as a basis for designing or modifying otherstructures for carrying out the same purposes of the present inventionand that such other structures so not depart from the spirit and scopeof the invention is its broadest form.

BRIEF DESCRIPTION OF THE DRAWINGS

Other aspects, features, and advantages of the present invention willbecome more filly apparent from the following detailed description, theappended claim, and the accompanying drawings in which:

FIG. 1 shows a graph depicting the change in surface refractive index asa function of electron beam dosage while maintaining current and energyconstant;

FIG. 2 shows a graph depicting the change in sample thickness as afunction of electron beam dosage while maintaining current and energyconstant;

FIG. 3 schematically depicts in FIGS. 3A, 3B, 3C, 3D and 3E severalaromatic chemical structures that can be used as starting materials;

FIG. 4 shows a schematic view of a large area electron beam exposureapparatus;

FIG. 5 shows the operation of the electron source;

FIG. 6 shows a schematic view of representative embossed structures 6A,6B and 6C;

FIG. 7 shows in FIGS. 7A, 7B, and 7C schematic views of forming anoptical material layer with a higher refractive index;

FIG. 8 shows in FIGS. 8A, 8B, 8C and 8D schematic views of forming aninterference filter;

FIG. 9 shows in FIGS. 9A and 9B schematic views of forming a multiplelayer interference filter;

FIG. 10 shows in FIGS. 10A, 10B, 10C, 10D and 10E schematic views offorming an optical material layer with multiple higher refractiveindexes;

FIG. 11 shows in FIGS. 11A, 11B, and 11C schematic views of forming anoptical material layer with a higher gradient refractive index;

FIG. 12 shows in FIGS. 12A, 12B, and 12C schematic views of forming amicrolens array;

FIG. 13 shows in FIGS. 13A and 13B schematic views of generatinggradients with supported films using embossed masks;

FIG. 14 shows in FIGS. 14A, 14B, and 14C schematic views of forming adiffraction grating;

FIG. 15 shows in FIGS. 15A and 15C schematic views of off axis exposuresand the resulting optical structures;

FIG. 16 shows in FIGS. 16A, 16B, 16C, 16D and 16E schematic views ofsequential exposures creating binary diffractive optical elementstructures;

FIG. 17 shows in FIGS. 17A, 17B, 17C and 17D schematic views of forminga waveguide;

FIG. 18 shows in FIGS. 18A, 18B, 18C and 18D schematic views of formingwaveguides from the patterned surface of the optical materials;

FIG. 19 shows in FIGS. 19A, 19B and 19C schematic views of forming anembedded waveguide with blazed surface diffraction gratings;

FIG. 20 shows in FIGS. 20A, 20B, 20C, and 20D schematic views of dualsided exposure techniques for forming a waveguide;

FIG. 21 shows an isometric view of representative multi-layeredapplications of the invention; and

FIG. 22 shows in FIGS. 22A, 22B, 22C, and 22D schematic views of formingan optical fiber waveguide.

DETAILED DESCRIPTION OF THE INVENTION

The exposure of selected optical materials to electron beam irradiationcan convert the existing material into a new state which exhibits moredesirable optical and mechanical properties not present in theun-irradiated material. An example of this can be seen in FIGS. 1 and 2which shows a plot of surface refractive index as a function of electrondosage and overall thickness respectively in a uniformly irradiatedsample as a function of electron dosage for several amorphousfluoropolymers. The new optical material was created only by exposure tothe electron beam. The introduction of extra bonds within, in this case,a high polymer results in a large refractive index change. Thisconversion can be done selectively in three dimensions in either acontinuous or periodic manner in normally non-reactive material systemsincluding oil, waxes, monomers, oligomers, and high polymers such that anumber of optically useful devices can be easily fabricated.

Typically, the prior art method of forming a waveguide, optical fiber,gradient index lens, diffraction grating beam-splitter, or interferencefilter required the use of optical polymers containing photoinitiators,subtractive techniques such as reactive ion etching, or bondingdissimilar materials together with glue layers. In the first case,involving the use of photoinitiators because the wavelength of theradiation typically used to activate the photoinitiator systems createsnear-field interference patterns (exhibiting textures on the order ofthe wavelengths trying to be propagated within the device) scatteringlosses results. These interference patterns are typically superimposedon the guiding structures used in splitters and other optical devicesleading to bridging and striation within the films, all of which resultin losses. The inventive use of electron beam processes eliminatesinterference effects since the equivalent wavelength (of the electronbeam) is orders of magnitude less than typical optical exposure tools.

The electron beam imparts sufficient energy to the chemical bonds tocreate scissions, which leads to the formation of additional networkingbonds as these reactive entities recombine within the material. Thechange in refractive index is due to the process of scission andreformation and (to a lesser extent) due to the extraction of lowmolecular weight components that are volatilized by the e-beam that areremoved by the vacuum system. Due to this dual process, conditions canbe created in which the index of refraction can be higher or lower thanthe index of refraction of the starting material cured usingconventional means. This allows a wide range of new materials to beselectively created having improved properties for optical applications.

Examples of the optical starting materials that can be converted usingthis approach include spin-on glasses, polymers, monomers, oligomers,waxes, and oils. These materials do not outgas significantly in softvacuum (10-50 millitorr). Other optically useful materials includecomposites and mixtures including inorganic/organic suspensions,polymers containing organometallics, and sol-gels. Since the formationof bonds does not require an additive such as a photoinitiator, therange of available material blends is large.

Preferred optical materials include the following: Typical spin-on glassmaterials include methylsiloxane, methylsilsesquioxane, phenylsiloxane,phenylsilsesquioxane, methylphenylsiloxane, methylphenylsilsesquioxane,and silicate polymers. Spin-on glass materials also includehydrogensiloxane polymers of the general formula(H_(0-1.0)SiO_(1.5-2.0))_(x) and hydrogensilsesquioxane polymers, whichhave the formula (HSiO_(1.5))_(x), where x is greater than about 8. Alsoincluded are copolymers of hydrogensilsesquioxane andalkoxyhydridosiloxane or hydroxyhydridosiloxane. Spin-on glass materialsadditionally include organohydridosiloxane polymers of the generalformula (H_(0-1.0)SiO_(1.5-2.0))_(n)(R_(0-1.0)SiO_(1.5-2.0))_(m), andorganohydridosilsesquioxane polymers of the general formula(HSiO_(1.5))_(n)(RSiO_(1.5))_(m), where m is greater than 0 and the sumof n and m is greater than about 8 and R is alkyl or aryl.

Typical polymer optical materials include halogenated polyalkylenes,preferred fluorinated an/or chlorinated polyalkylens, more preferredchlorofluoropolyalkylens, and most preferred are the fluorinatedpolyalkylenes among which are included: polytetrafluoroethane(ethylene), polytrifluoroethylene, polyvinylidene fluoride,polyvinylfluoride, copolymers of fluorinated ethylene or fluorinatedvinyl groups with non-fluorinated ethylenesor vinyl groups, andcopolymers of fluorinated ethylenes and vinyls with straight orsubstituted cyclic fluoroethers containing one or more oxygens in thering. Also included in the most preferred polymers are poly(fluorinatedethers) in which each linear monomer may contain from one to four carbonatoms between the ether oxygens and these carbons may be perfluorinated,monofluorinated, or not fluorinated.

Also included in the most preferred polymer optical materials arecopolymers of wholly fluorinated alkylenes with fluorinated ethers,partly fluorinated alkylenes with wholly fluorinated ethers, whollyfluorinated alkylenes with partly fluorinated ethers, partly fluorinatedalkylenes with partly fluorinated ethers, non-fluorinated alkylenes withwholly or partly fluorinated ethers, and non-fluorinated ethers withpartly or wholly fluorinated alkylenes.

Also included among the most preferred polymer optical materials arecopolymers of alkylenes and ethers in which one kind of the monomers iswholly or partly substituted with chlorine and the other monomer issubstituted with fluorine atoms. In all the above, the chain terminalgroups may be similar to those in the chain itself, or different.

Also among the most preferred polymer optical materials are includedsubstituted polyacrylates, polymethacrylates, polyitaconates,polymaleates, and polyfumarates, and their copolymers, in which theirsubstituted side chains are linear with 2 to 24 carbon atoms, and theircarbon atoms are fully fluorinated except for the first one or twocarbons near the carboxyl oxygen atom such as Fluoroacrylate,Fluoromethacrylate and Fluoroitaconate.

Among the more preferred polymer optical materials, one includesfluoro-substituted polystyrenes, in which the ring may be substituted byone or more fluorine atoms, or alternatively, the polystyrene backboneis substituted by up to 3 fluorine atoms per monomer. The ringsubstitution may be on ring carbons No. 4, 3, 2, 5, or 6, preferably oncarbons No. 4 or 3. There may be up to 5 fluorine atoms substitutingeach ring.

Among the more preferred polymer optical materials, one includesaromatic polycarbonates, poly(ester-carbonates), polyamids andpoly(esteramides), and their copolymers in which the aromatic groups aresubstituted directly by up to four fluorine atoms per ring one by one onmore mono or trifluoromethyl groups such as shown in FIGS. 3A, 3B, 3C,3D and 3E.

Among the more preferred polymer optical materials, arefluoro-substituted poly(amic acids) and their corresponding polyimides,which are obtained by dehydration and ring closure of the precursorpoly(amic acids). The fluorine substitution is effected directly on thearomatic ring. Fluoro-substituted copolymers containingfluoro-substituted imide residues together with amide and/or esterresidues are included.

Also among the more preferred polymer optical materials are parylenes,fluorinated and non-fluorinated poly(arylene ethers), for example thepoly(arylene ether) available under the tradename FLARE™ fromAlliedSignal Inc., and the polymeric material obtained fromphenyl-ethynylated aromatic monomers and oligomers provided by DowChemical Company under the tradename SiLK™, among other materials.

In all the above, the copolymers may be random or block or mixturesthereof.

The method of creating optical materials with changed refractive indexesfrom these conventional spin-on glass and polymer materials, accordingto the present invention, is depicted in FIGS. 4 and 5. A substrate 127is placed in a vacuum chamber 120 at a pressure of 15 to 40 millitorrand underneath an electron source at a distance from the sourcesufficient for the electrons to generate ions in their transit betweenthe source and the substrate surface. The electrons can be generatedfrom any type of source that will work within a soft vacuum (15 to 40milliTorr) environment. A source particularly well suited for this isdescribed in U.S. Pat. No. 5,003,178, the disclosure of which is herebyincorporated into this specification by reference. This is a largeuniform and stable source that can operate in a soft vacuum environment.The cathode 122 emits electrons. The electrons are accelerated by thefield between the cathode and anode 126. The potential between these twoelectrodes is generated by the high voltage supply 129 applied to thecathode 122 and the bias voltage supply 130 applied to the anode 126.The electrons irradiate the starting optical material layer 128 coatedon the substrate 127. The starting optical material layer 128 may be anyof the materials previously mentioned or the spin-on glass or polymermaterials described above. An electron energy is selected to eitherfully penetrate or partially penetrate the full thickness of startingoptical material layer 128. For example, a large area electron beamenergy of 9 keV is used to penetrate a 6000 Angstrom thick film.Infrared quartz lamps 136 irradiate the bottom side of the substrateproviding heating independent from the electron beam. A variable leakvalve or mass flow controller, identified by reference 132, is utilizedto leak in a suitable gas to maintain the soft vacuum environment.

Referring to FIG. 5, electrons 145 traversing the distance 146 betweenthe anode 126 and the substrate 127 ionize the gas molecules located inregion 138 generating positive ions. These positive ions 143 are thenattracted back to the anode 126 where they can be accelerated, asindicated at 142, toward the cathode to generate more electrons. Thestarting optical material layer 128 on the substrate 127 is an insulatorand will begin to charge negatively, as indicated at 147, under electronbombardment. However, the positive ions near the substrate surface willbe attracted to this negative charge and will then neutralize it. Thelamps 136 (FIG. 4) irradiate and heat the starting optical materiallayer or substrate thereby controlling its temperature. Since thestarting optical material layer is in a vacuum environment and thermallyisolated, the starting optical material layer can be heated or cooled byradiation. If the lamps are extinguished, the starting optical materiallayer will radiate away its heat to the surrounding surfaces and gentlycool. In one embodiment of the invention, the starting optical materiallayer is simultaneously heated by the infrared lamps and irradiated bythe electron beam throughout the entire process.

In the present method, a solution containing a spin-on glass or polymermaterial is deposited on substrate 127 by conventional means such asspin-coating or, alternatively, spray-coating or dip-coating to formstarting optical material layer 128. Substrate 127 represents any layeror stack of layers on a multiple-optical layer device. The coatedsubstrate is continuously irradiated with electrons until a sufficientdose has accumulated to attain the desired change in the material andaffect starting optical material layer properties such as refractiveindex. A total dose of between 10 and 100,000 microCoulombs per squarecentimeter (μC/cm²) may be used. Preferably, a dose of between 100 and10,000 μC/cm² is used, and most preferably a dose of between about 2,000and 5,000 μC/cm² is used. The electron beam is delivered at an energy ofbetween 0.1 and 100 keV, preferably at an energy between 0.5 and 20 keV,and most preferably at an energy between 1 and 10 keV. The electron beamcurrent ranges between 0.1 and 100 mA, and more preferably between 0.25and 30 mA. The entire electron dose may be delivered at a singlevoltage. Alternatively, particularly for starting optical materiallayers thicker than about 0.25 μm, the dose is divided into steps ofdecreasing voltage, which provides a “uniform dose” process in which thematerial is irradiated from the bottom up. The higher energy electronspenetrate deeper into the starting optical material layer. In this way,the depth of electron beam penetration is varied during the electronexposure process resulting in a uniform energy distribution throughoutthe starting optical material layer. The variation allows for volatilecomponents, such as solvent residues, to leave the starting opticalmaterial layer without causing any damage such as pinholes or cracks.This also attains uniform refractive index throughout the layer exposed.Alternatively, the electron energy can be varied to achieve a precisedose and refractive index change spatially within the material.

During the electron beam exposure process, the starting optical materiallayer is kept at a temperature between 10 degrees Celsius and 1000degrees Celsius. Preferably, the wafer temperature is between 30 degreesCelsius and 500 degrees Celsius. For some waxes and other low meltingpoint materials low temperatures are utilized (25 degrees to 175 degreesCelsius). The infrared quartz lamps 36 are on continuously until thestarting optical material layer temperature reaches the desired processtemperature. The lamps are turned off and on at varying duty cycle tocontrol the starting optical material layer temperature. Typicalbackground process gases in the soft vacuum environment includenitrogen, argon, oxygen, ammonia, forming gas, helium, methane,hydrogen, silane, and mixtures thereof. For many starting opticalmaterials, a non-oxidizing processing atmosphere is used. For otherapplications, an oxidizing atmosphere would be appropriate. The optimalchoice of electron beam dose, energy, current, processing temperature,and process gas depends on the composition of the starting opticalmaterial, spin-on glasses or polymer material.

The optical starting material may be deposited onto a suitablesubstrate. Typical substrates include glass, silicon, metal, and polymerfilms. Substrates can also be porous, textured or embossed. Depositionon substrates may be conducted via conventional spin coating, dipcoating, roller coating, spraying, embossing, chemical vapor depositionmethods, or meniscus coating methods, which are well known in the art.Spin coating on substrates is most preferred. Multiple layers of thesame optical materials are also preferred. Layer thicknesses typicallyrange from 0.01 to 20 microns. 1 to 10 microns is preferred. In anotherembodiment of the invention, the optical starting material is formedinto a supported film similar to pellicles used in semiconductorapplications. In this case, starting optical material layers may beformed by casting, spin coating, and dip coating, lifted off thesubstrate and attached to a frame for handling. In addition, extrudedstarting optical material layers can be attached to a frame, all ofwhich are well known in the art. Casting, with lift-off and frameattachment is preferred. Single starting optical material layers exhibitthicknesses ranging from 1 micron to 10 microns. Once the article hasbeen formed, the exposure equipment needs to be selected.

Exposure of the starting optical material layer can be done with anytype of low energy electron source, preferably in the range of 1 to 50keV. Soft vacuum (15 to 40 milliTorr) is also preferred for removal ofvolatiles and usage of low keV electrons. In the preferred embodiment ofthis invention, the starting optical material, either on a substrate oras supported film, is selectively exposed to the electron beam andheated using the IR lamps. Selective heating is also preferred. The IRlamps typically operate from room temperature to 400 degrees Celsius.Most optical materials exhibit different e-beam irradiation responsesdepending on the temperature of the material. In-situ monitoring of theexposure process is included in this invention such as monitoringgrating spectral response concerning side lobes during exposure. Otherfunctions such as transmission loss, polarization sensitivity, and backreflections can all be monitored during exposure and used in a feedbackloop to the exposure parameters. In-situ feedback during exposure is anembodiment of this invention. Various gases can be introduced during theirradiation process. It has been shown that these gases can be reactedinto the starting optical material layer depending on the material andexposure conditions. Introduction of a reactive or non-reactive gas intothe starting optical material layer during exposure is a furtherembodiment of this invention. Radial exposure conditions, as well asother non-flat configurations, are embodiments of this invention as wellas modification of the electron field using external means such asmagnetic fields. Once the equipment is selected, the exposure conditionsare selected.

Typically the starting optical material layer is exposed to a sequentialseries of kinetic energies generating a particular distribution of bonddensities within the optically useful material. Based on the opticalmaterial's particular e-beam response, temperature distribution withinthe material, kinetic energy distribution of the electrons, and densityof the material, a range of refractive index changes can be generated.Preferred starting optical material layer change includes 3 dimensionalcomplex index of refraction. Exposure can be done through an aperturemask as known in the art or by embossing or forming an absorptive maskdirectly on the starting optical material layer or on a thin carrierfilm support above the starting optical material layer. In the case ofstarting optical material layers, dual sided processing can be used. Themask can be either sacrificial or permanent depending on theapplication. In this embodiment of the invention, rather than forming abinary system a gradient of exposure can be generated.

As shown in FIG. 6, a variety of starting optical material layerstructures can be formed using embossing or photolithography steps knownin the art. During exposure the areas covered by the mask wouldproportionally absorb electrons as a function of the embossed thickness.As stated earlier, both the dosage and energy distribution is affectedby this approach. But it has been demonstrated that a variety ofgradient structures can be generated using this patterning technique anda number of the examples include this approach. In addition, because thestarting optical material layer or a thin membrane supports the mask,multiple sequential masks are not required. In the case of embossed ortextured starting materials, the need for a mask can be totallyeliminated. The embossed structure is irradiated such that thepenetration depth is less than feature height. The result is a region ofhigher refractive index on pedestal after overcoating the resultingwaveguide structure appears. In addition, a waveguide can be created ona grating surface. Because the irradiation condition determines thepenetration depth, the resulting waveguide will follow the rapidmodulation in the grating. Multiple layered configurations are alsoembodiments of this invention and will be shown in some of the followingexamples as will the use of this technique to couple closely spacedwaveguides and other optical devices. A further embodiment involves theuse of the proximity effect to directly form tapered waveguides. Due tospreading as a function a depth that occurs, an array of micro-opticalwaveguides can be formed in a film. Once the sample is exposed,fabrication into a device can commence.

The electron beam apparatus and method can be used to change therefractive index for an entire layer of optical material.

As shown in FIG. 7A, the substrate 200 has an upper surface 202 and alower surface 204. The starting optical material layer 206 has an uppersurface 208 and a lower surface 210. The lower surface 210 of thestarting optical material layer is deposited, bonded, coated, orotherwise positioned on the upper surface 202 of the substrate. Thestarting optical material layer 206 will have an original index ofrefraction n₀.

As shown in FIG. 7B, a large area electron beam 212 is incident at aperpendicular angle to the upper surface 208 of the optical materiallayer 206 and irradiates the optical material layer. Infrared radiationbeams 214 will heat the substrate 200 through the lower surface 204 and,by heat transfer through the substrate, will heat the starting opticalmaterial 206. The electron beam 212 fully penetrates the depth orthickness 218 of the optical material layer to the lower surface 210 ofthe optical material layer 206 and the upper surface 202 of thesubstrate 200.

As shown in FIG. 7C, the entire optical material layer 206, afterelectron beam irradiation and heating, will have a uniform index ofrefraction n₁, which is higher than the original index of refraction n₀of the starting optical material layer, through the full thickness 218of the optical material layer.

Alternately, the electron beam irradiation can form a gradient index ofrefraction from n_(0.1) to n₁ within the optical material layer 206. Theindex of refraction will increase from the lower surface 210 to theupper surface 208. The temperature of the substrate supporting thestarting optical material, the voltage of the electron beam, the dose ofthe electron beam, the duration and number of steps of the electronbeam, the use of oxidizing or non-oxidizing gases in the low vacuumatmosphere, can each separately, or in combination, be varied tofabricate a gradient index of refraction within the starting opticalmaterial.

The optical material layer can be removed from the substrate byconventional chemical, etching or physical means. Alternately, a releaselayer (not shown in this Figure) can be deposited on the substrate andthe starting optical material layer can be deposited on the releaselayer. The electron beam radiation and heat radiation will pass throughthe release layer without effecting the release layer or thetransformation of the starting optical material layer. After thetransformation process, the optical material layer can be lifted off thesubstrate by dissolving the release layer.

The electron beam apparatus and method can provide a layer of onerefractive index integral and adjacent to a layer of another refractiveindex with both layers formed of the same optical material.

As shown in FIG. 8A, the substrate 300 has an upper surface 302 and alower surface 304. The starting optical material layer 306 has an uppersurface 308 and a lower surface 310. The lower surface 310 of thestarting optical material layer is deposited, bonded, coated, orotherwise positioned on the upper surface 302 of the substrate. Thestarting optical material layer 306 will have an original index ofrefraction n₀ and a thickness 312.

As shown in FIG. 8B, a large area electron beam 314 is incident at aperpendicular angle to the upper surface 308 of the optical materiallayer 306 and irradiates the optical material layer. Infrared radiationbeams 316 will heat the substrate 300 through the lower surface 304 and,by heat transfer through the substrate, will heat the starting opticalmaterial 306. The electron beam 314 partially penetrates the opticalmaterial layer to a depth or thickness 318 from the upper surface 308between the upper surface 308 and the lower surface 310 of the opticalmaterial layer. The penetration depth 318 is less than the thickness 312of the optical material layer.

As shown in FIG. 8C, the partial penetration of the electron beamirradiation divides the optical material into a first sub-layer and asecond sub-layer. The optical material layer 306 has a second or uppersub-layer 320 having an upper surface 308 and a lower surface 322 and afirst or lower sub-layer 324 having an upper surface 326 and a lowersurface 310. The lower surface 322 of the upper sub-layer is on theupper surface 326 of the lower sub-layer. The lower surface 310 of thelower sub-layer is on the upper surface 302 of the substrate. Since thestarting optical material layer is one layer, after electron beamirradiation, the second sub-layer is integral and positioned adjacentand on top of the first sub-layer within the optical material layer.

The second or upper optical material sub-layer 320 will have an index ofrefraction n₁, which is higher than the original index of refraction n₀of the starting optical material layer 306. The lower surface 322 of theupper sub-layer is at the irradiation penetration depth 318 of theelectron beam. The upper sub-layer will have a thickness equivalent tothe penetration depth of the electron beam.

The first or lower optical material sub-layer 324, which was notirradiated by the electron beam, has the original index of refraction n₀of the starting optical material 306. The lower sub-layer will have athickness 328 equivalent to the original thickness 312 of the startingoptical material less the thickness 318 of the upper sub-layer.

The optical material layer will have a second sub-layer with a highrefractive index on top of a first sub-layer with a lower refractiveindex without fabrication by deposition, without an intervening adhesivelayer between the two sub-layers, and with both sub-layers being formedfrom the same optical material.

The depth of the penetrating electron beam and the resulting thicknessof the altered refractive index layer are determined by the dose,voltage and duration of the electron beam and accordingly can vary fromthe upper surface of the starting optical material layer to the lowersurface of the starting optical material layer.

The second or upper sub-layer 320 can alternately have a gradient indexof refraction. The temperature of the substrate supporting the startingoptical material, the voltage of the electron beam, the dose of theelectron beam, the duration and number of steps of the electron beam,the use of oxidizing or non-oxidizing gases in the low vacuumatmosphere, can each separately, or in combination, be varied tofabricate a gradient index of refraction within the starting opticalmaterial.

As shown in FIG. 8D, the optical material layer 306 can be removed fromthe substrate by conventional chemical, etching or physical means.Alternately, a release layer (not shown in this Figure) can be depositedon the substrate and the starting optical material layer can bedeposited on the release layer. The electron beam radiation and heatradiation will pass through the release layer without effecting therelease layer or the transformation of the starting optical materiallayer. After the transformation process, the optical material layer canbe lifted off the substrate by dissolving the release layer.

The optical material layer 306 will be inverted and deposited, bonded orpositioned on the surface 350 of an optical element 352. The uppersurface 308 of the second sub-layer will be attached to the uppersurface 350 of the optical element. The lower surface 310 of the firstsub-layer will be the outer surface of then optical material on theoptical element. The second sub-layer 324 is adjacent to the opticalelement 350 with the first sub-layer 320 being on the outside.

The sequence will be optical element 350, the second sub-layer 320 witha high refractive index and the first sub-layer 324 with a lowrefractive index. If the optical thickness 318 of the second sub-layer320 and the optical thickness 328 of the first sub-layer 324 are inquarter-wavelengths or whole number multiples of quarter wavelengths forthe light transmitted through or reflected from the optical element, thetwo sub-layers of the optical material will form an interference filterwhich can be an anti-reflection coating for the optical element or aheat reflective thermal control layer for the optical element or awavelength sensitive reflectance/transmittance interference filter forthe optical element 352.

An interference filter is formed by a high refractive index materiallayer on a substrate with a low refractive index material layer on thehigh refractive index material layer. The antireflection coating reducesreflected light by decreasing the refractive index difference betweenthe optical element next to the adjacent high refractive layer and theambient atmosphere next to the low refractive index layer. The heatreflective thermal control film transmits visible radiation whilereflecting infrared radiation. The wavelength sensitivereflectance/transmittance interference filter can reflect or transmitselected wavelengths of light or reflect or transmit ranges ofwavelengths of light.

The electron beam apparatus and method of the present invention allowsthe thickness of the low refractive sub-layer of the optical materialand the thickness of the high refractive sub-layer of the same opticalmaterial to be individually selected for use in an optical element. Thethicknesses can be fractions of wavelengths or ratios to each other.

As shown in FIG. 9A, a first starting optical material layer 400 isbonded, deposited, coated or positioned on a substrate 402. A large areaelectron beam (not shown) irradiates the first starting optical materiallayer while infrared beams (also not shown) heat the substrate and firststarting optical material layer. The first optical material layer 400will form a low refractive index sub-layer 404 and a high refractiveindex sub-layer 406.

A second starting optical material layer 408 is bonded, deposited,coated or positioned on the high refractive index sub-layer 406 of thefirst starting optical material layer 400. A large area electron beam(not shown) irradiates the second starting optical material layer whileinfrared beams (also not shown) heat the second starting opticalmaterial layer. The second optical material layer 408 will form a lowrefractive index sub-layer 410 and a high refractive index sub-layer412.

As shown in FIG. 9B, the first and second starting optical materiallayers 400 and 408 with the sub-layers can be removed from the substrateby the use of a release layer or by conventional chemical, etching orphysical means and inverted to form an optical element 414.

The resulting optical element 414 has alternating layers of high and lowrefractive index materials. The optical element can have multipleoptical material layers with multiple alternating layers of high and lowrefractive index materials formed by the electron beam apparatus andmethod of the present invention.

The starting optical material layers for the optical element can be thesame with the low refractive sub-layers sharing the same original indexof refraction. The high refractive sub-layers can have the same ordifferent indexes of refraction. The electron beam apparatus and methodcan form different indexes of refraction for the same optical materialbased on the temperature of the substrate supporting the startingoptical material, the voltage of the electron beam, the dose of theelectron beam, the duration and number of steps of the electron beam,and the use of oxidizing or non-oxidizing gases in the low vacuumatmosphere.

As noted earlier, the thicknesses of the layers of high and lowrefractive index materials can be individually selected for eachsub-layer in the optical element. The optical element can have layers ofthe original starting optical material without its refractive indexchanged and solid layers (without sub-layers) of optical material with araised refractive index like the optical material 206 of FIG. 7.

The starting optical material layers in the optical element can bedifferent optical materials providing different refractive indexes forthe alternating layer of high and low refractive index materials.

The optical element of multiple optical material layers with multiplealternating layers of high and low refractive index materials, with arange of refractive indexes and thicknesses and optical materials, canbe used as a conventional diffraction grating, a conventionalinterference filter, or a conventional beam-splitter, as is known in theart.

The optical element of multiple optical material layers with multiplealternating layers of high and low refractive index materials can beused as an interference filter, which can be an anti-reflection coatingor a heat reflective thermal control layer or a wavelength sensitivereflectance/transmittance interference filter.

The temperature of the substrate supporting the starting opticalmaterial, the voltage of the electron beam, the dose of the electronbeam, the duration and number of steps of the electron beam, the use ofoxidizing or non-oxidizing gases in the low vacuum atmosphere, can eachseparately, or in combination, be varied to fabricate a gradient indexof refraction within the optical material.

The electron beam apparatus and method can provide adjacent integralmultiple layers of different increasing refractive indexes with themultiple layers formed of the same optical material.

As shown in FIG. 10A, the substrate 500 has an upper surface 502 and alower surface 504. The starting optical material layer 506 has an uppersurface 508 and a lower surface 510. The lower surface 510 of thestarting optical material layer is deposited, bonded, coated, orotherwise positioned on the upper surface 502 of the substrate. Thestarting optical material layer 506 will have an original index ofrefraction n₀ and a thickness 512.

As shown in FIG. 10B, a first large area electron beam 514 is incidentat a perpendicular angle to the upper surface 508 of the opticalmaterial layer 506 and irradiates the optical material layer. Infraredradiation beams 516 will heat the substrate 500 through the lowersurface 504 and, by heat transfer through the substrate, will heat thestarting optical material 506. The first electron beam 514 partiallypenetrates the optical material layer to a depth or first thickness 518from the upper surface 508 between the upper surface 508 and the lowersurface 510 of the optical material layer. The first penetration depth518 is less than the thickness 512 of the optical material layer.

As shown in FIG. 10C, the partial penetration of the electron beamirradiation divides the optical material into a first sub-layer and atransitional sub-layer. The optical material layer 506 has atransitional or upper sub-layer 520 having an upper surface 508 and alower surface 522 and a first or lower sub-layer 524 having an uppersurface 526 and a lower surface 510. The lower surface 522 of thetransitional sub-layer is on the upper surface 526 of the lowersub-layer. The lower surface 510 of the lower sub-layer is on the uppersurface 502 of the substrate.

The transitional sub-layer 520 will have an index of refraction n₁,which is higher than the original index of refraction of the startingoptical material layer 506. The lower surface 522 of the transitionalsub-layer is at the first irradiation penetration depth 518 of theelectron beam. The first sub-layer 524, which was not irradiated by theelectron beam, has the original index of refraction n₀ of the startingoptical material 506.

As shown in FIG. 10D, a second large area electron beam 528 is incidentat a perpendicular angle to the upper surface 508 of the transitionalsub-layer 520 and irradiates the optical material in the transitionalsub-layer. Infrared radiation beams 530 will heat the substrate 500through the lower surface 504 and, by heat transfer through thesubstrate 500 and the first sub-layer 524, will heat the transitionalsub-layer 520.

The second electron beam 528 partially penetrates the optical materialof the transitional sub-layer layer 520 to a depth or second thickness532 from the upper surface 508 between the upper surface 508 of thetransitional sub-layer 526 and the upper surface of the first sub-layer524. The second irradiation penetration depth 532 is less than thethickness of the optical material 512 and is less than the firstirradiation penetration depth 518. The second electron beam 528 does notpenetrate the first sub-layer 524, only partially penetrating thetransitional sub-layer 520.

As shown in FIG. 10E, the partial penetration of the second electronbeam irradiation divides the transitional sub-layer of optical materialinto a second sub-layer and a third sub-layer. The optical material willhave a third or upper sub-layer 534 having an upper surface 508 and alower surface 536 and a second or middle sub-layer 538 having an uppersurface 540 and a lower surface 522. The lower surface 536 of the thirdsub-layer 534 is on the upper surface 540 of the second sub-layer 538.The lower surface 522 of the second sub-layer 538 is on the uppersurface 526 of the first sub-layer 524.

Since the starting optical material layer is one layer, after electronbeam irradiation, the third, second and first sub-layer are integralwith third sub-layer positioned adjacent to and on top of the secondsub-layer and the second sub-layer positioned adjacent to and on top ofthe first sub-layer within the optical material layer.

The third sub-layer 534 will have an index of refraction n₂, which ishigher than the index of refraction n₁ of the second sub-layer 538, andhigher than the index of refraction n₀ of the first sub-layer 524 andthe starting optical material layer 506. The lower surface 536 of thethird sub-layer 534 is at the second irradiation penetration depth 518of the electron beam. The third sub-layer 534 has been exposed to thefirst and second electron beam. The second sub-layer 538 has only beenexposed to the first electron beam. The first sub-layer 524, which wasnot irradiated by the second electron beam nor the first electron beam,has the original index of refraction n₀ of the starting optical material506.

The third sub-layer 534 will have a thickness equivalent to the secondpenetration depth 532 of the second electron beam. The second sub-layer538 will have a thickness equivalent to the first penetration depth 518of the first electron beam less the second penetration depth 532 of thesecond electron beam. The first sub-layer 524 will have a thicknessequivalent to the original thickness 512 of the starting opticalmaterial less the thickness of the second and third sub-layers (orequivalent to the original thickness of the starting optical material512 less the thickness of the first penetration depth 518).

The optical material 506 has a first or lower sub-layer 524 with a firstindex of refraction, a second or middle sub-layer 538 with a secondindex of refraction higher than the first index of refraction and athird or upper sub-layer 534 with a third index of refraction higherthan the second index of refraction and higher than the first index ofrefraction.

The optical material layer 506 has sub-layers of progressively higherindexes of refraction without fabrication by deposition, without anintervening adhesive layer between the layers, and with all the layersbeing formed from the same material.

The optical material layer 506 can be removed from the substrate byconventional chemical, etching, physical means or the use of a releaselayer, as discussed previously. After release, the optical materiallayer can be inverted. The inverted optical material layer 506 hassub-layers of progressively lower indexes of refraction withoutfabrication by deposition, without an intervening adhesive layer betweenthe layers, and with all the layers being formed from the same material.

The optical material layer 506 can be used as an interference filter, asdiscussed previously or formed into multiple alternating layers to beused as a diffraction grating or beam-splitter, also as discussedpreviously.

The temperature of the substrate supporting the starting opticalmaterial, the voltage of the electron beam, the dose of the electronbeam, the duration and number of steps of the electron beam, the use ofoxidizing or non-oxidizing gases in the low vacuum atmosphere, can eachseparately, or in combination, be varied to fabricate a gradient indexof refraction within the starting optical material.

Alternately, the multiple electron beam irradiation can form multiplesub-layers of increasing uniform or gradient indexes of refraction witheach sub-layer having an index of refraction greater than the originalindex of refraction n₀ of the starting optical material. There would beno sub-layers of just the original starting optical material. Everysub-layer would be irradiated with electron beams to increase its indexof refraction.

As shown in FIG. 11A, the substrate 600 has an upper surface 602 and alower surface 604. The starting optical material layer 606 has an uppersurface 608 and a lower surface 610. The lower surface 610 of thestarting optical material layer is deposited, bonded, coated, orotherwise positioned on the upper surface 602 of the substrate. Thestarting optical material layer 606 will have an original index ofrefraction n₀.

As shown in FIG. 11B, a large area electron beam 612 is incident at aperpendicular angle to the upper surface 608 of the optical materiallayer 606 and irradiates the optical material layer. Infrared radiationbeams 614 will heat the substrate 600 through the lower surface 604 and,by heat transfer through the substrate, will heat the starting opticalmaterial 606. The electron beam 612 fully penetrates the depth orthickness 618 of the optical material layer to the lower surface 610 ofthe optical material layer 606 and the upper surface 602 of thesubstrate 600.

The electron beam provides precisely controlled electron doses atselected energies at differing relative depths causing an unequaldistribution of electron energy along the depth of the starting opticalmaterial which results in varying indexes of refraction along the depthof the material.

As shown in FIG. 11C, the entire optical material layer 606, afterelectron beam irradiation and heating, will have a gradient index ofrefraction which varies from n₁ to n₂ by depth, with the upperrefractive index n₂ closer to the upper surface being higher than thelower refractive index n₁ closer to the lower surface. Both refractiveindexes n₁ to n₂ are higher than the original index of refraction n₀,through the full depth 618 of the optical material layer.

The refractive index of the optical material 606 of FIG. 8 can vary byprogressions other than straight line gradient, such as exponential orlogarithmic, which are illustrative examples but not an exhaustive listof examples.

An embossing structure can be used with the electron beam apparatus andmethod to pattern the refractive index areas within the same opticalmaterial layer.

As shown in FIG. 12A, the substrate 700 is a support ring with an uppersurface 702 and a lower surface 704. The starting optical material layer706 has an upper surface 708 and a lower surface 710. A small portion712 of the lower surface 710 of the starting optical material layer isdeposited, bonded, coated, or otherwise positioned on the upper surface202 of the substrate support ring. A large portion 714 of the lowersurface 710 of the starting optical material layer remains exposed. Thesupport ring can substitute for a substrate layer in this and otherembodiments of the present invention. The starting optical materiallayer 706 will have an original index of refraction n₀ and a thickness716.

As shown in FIG. 12B, an embossed structure 718 is formed of photoresistand has a series of concave surfaces 720 on its upper surface 722. Thelower surface 724 of the embossed structure 718 is flat and deposited orpositioned on the upper surface 708 of the starting optical material706.

A large area electron beam 726 is incident at a perpendicular angle tothe upper surface 722 of the embossed structure 718 and irradiates theembossed structure 718 and the optical material layer 706. Infraredradiation beams 728 will heat the starting optical material 706 throughthe exposed portion 714 of the lower surface 710 of the starting opticalmaterial layer 706.

The electron beam 726 fully penetrates the embossed structure 718 andpartially penetrates the starting optical material layer 706 between thebetween the upper surface 708 and the lower surface 710 of the opticalmaterial layer.

As shown in FIG. 12C, the embossing structure 718 of photoresist isremoved by conventional means. The optical material layer 706 is removedfrom the substrate support rings 700 by conventional chemical, etching,physical means or the use of a release layer, as discussed previously.

The partial penetration of the electron beam irradiation formssemi-circular concave areas 730 having a varying thickness 732 from theupper surface 708 extending into the optical material 706. These areas730 will have an index of refraction of either n₂ to n₁ or n₁, which ishigher than the original index of refraction n₀ of the starting opticalmaterial layer 706. The lower surface 734 of the areas is at theirradiation penetration depth of the electron beam through the embossingstructure and into the optical material layer. The varying thickness ofthe areas is in inverse proportion to the upper surface of the embossedstructure.

The surrounding optical material sub-layer 706, which was not irradiatedby the electron beam, has the original index of refraction n₀ of thestarting optical material layer. The lower sub-layer will have athickness 736 equivalent to the original thickness 716 of the startingoptical material less the thickness 732 of the areas 730.

Since the starting optical material layer is one layer, after electronbeam irradiation, the areas 730 of high refractive index are integraland positioned adjacent to the surrounding optical material sub-layer706 within the optical material layer.

The areas 730 of high refractive index form a microlens structure in theoptical material layer 706. The microlens structure is in inverse imageof the embossing structure.

The optical material layer with a lower refractive index will have amicrolens structure with a high refractive index without fabrication bydeposition, without an intervening adhesive layer between the structureand layer, and with both structure and layer being formed from the sameoptical material.

The depth of the penetrating electron beam and the resulting thicknessof the altered refractive index layer are determined by the dose,voltage and duration of the electron beam and accordingly can vary fromthe upper surface of the starting optical material layer to the lowersurface of the microlens structure.

The electron beam can provide a uniform refractive index n₁ to theresulting irradiated optical material of the microlens structure, asdiscussed in FIG. 8, to form a binary diffractive lens. Or the electronbeam can provide a gradient refractive index n₂ to n₁ to the resultingirradiated optical material of the microlens structure, as discussed inFIG. 11, to form a gradient index (GRIN) lens. The gradient refractiveindex lens will have a refractive index which varies from n₁ to n₂ bydepth, with the upper refractive index n₂ closer to the upper surface ofthe optical material being higher than the lower refractive index n₁closer to the lower surface of the optical material. Both refractiveindexes n₁ to n₂ are higher than the original index of refraction n₀, ofthe starting optical material layer. The GRIN array and the opticalmaterial layer can be lifted off the substrate by dissolving the releaselayer.

As shown in an alternate embossed structure embodiment of FIG. 13A, awax embossed structure 800 of 120 degree included angle prisms 802 at aregular pitch interval is deposited on the upper surface 804 of thestarting optical material 806. The starting optical material 806 ispositioned on a substrate support ring 808. The electron beam apparatusand method are the same as in FIG. 9.

A large area electron beam 810 is incident at a perpendicular angle tothe upper surface 812 of the embossed structure 800 and irradiates theembossed structure 800 and the optical material layer 806. Infraredradiation beams 814 will heat the starting optical material 806 throughthe exposed portion 816 of the lower surface 818 of the starting opticalmaterial layer 806.

The electron beam 810 fully penetrates the embossed structure 800 andpartially penetrates the starting optical material layer 806 between thebetween the upper surface 804 and the lower surface 818 of the opticalmaterial layer.

As shown in FIG. 13B, the embossing structure 800 of wax is removed byconventional means. The optical material layer 806 is removed from thesubstrate support rings 808 by conventional chemical, etching, physicalmeans or the use of a release layer, as discussed previously.

The partial penetration of the electron beam irradiation forms arefractive index gradient patterned area 820, triangular incross-section, from the upper surface 804 extending into the opticalmaterial 806. These triangular areas 820 will have a varying refractiveindex from n₁ to n₂ by depth, with the upper refractive index n₂ closerto the upper surface 804 being higher than the lower refractive index n₁closer to the lower surface 818. Both refractive indexes n₁ to n₂ arehigher than the original index of refraction n₀. The lower surface 822of the triangular areas is at the irradiation penetration depth of theelectron beam through the embossing structure and into the opticalmaterial layer. The varying thickness of the areas is in inverseproportion to the upper surface 812 of the embossed structure. The indexgradient is in inverse image of the embossing structure.

The surrounding optical material sub-layer 806, which was not irradiatedby the electron beam, has the original index of refraction n₀ of thestarting optical material layer.

Since the starting optical material layer is one layer, after electronbeam irradiation, the areas 820 of high refractive index are integraland positioned adjacent to the surrounding optical material sub-layer806 within the optical material layer.

The index gradient 820 can be used as a diffraction grating or abeam-splitter. Light propagating within the alternating sections of lowand varying high refractive index in the resulting optical materiallayer will be extracted by the index gradient.

The electron beam can provide a uniform refractive index n₁ to theresulting irradiated optical material of the index gradient structure,as discussed in FIG. 11, to form a refractive lens.

An aperture mask can be used with the electron beam apparatus and methodto provide a section of one refractive index integral and adjacent to asection of another refractive index with both sections formed of thesame optical material.

As shown in FIG. 14A, the substrate 900 has an upper surface 902 and alower surface 904. The starting optical material layer 906 has an uppersurface 908 and a lower surface 910. The lower surface 910 of thestarting optical material layer is deposited, bonded, coated, orotherwise positioned on the upper surface 902 of the substrate. Thestarting optical material layer 906 will have an original index ofrefraction n₀ and a thickness 912.

As shown in FIG. 14B, an aperture mask 914 is positioned between theelectron beam source (not shown in this Figure) and the starting opticalmaterial layer 906. The mask 914 has an upper surface 916 and apertures918.

A large area electron beam 920 is incident at a perpendicular angle tothe upper surface 908 of the optical material layer 906 through theapertures 918 of the mask 914 and irradiates the optical material layerthrough the mask apertures 918. The electron beam 920 will be absorbed,or otherwise blocked, by the surface 916 of the mask 914 but will betransmitted through the apertures 918. Infrared radiation beams 922 willheat the substrate 900 through the lower surface 904 and, by heattransfer through the substrate, will heat the starting optical material906.

The electron beam 920 fully penetrates the depth or thickness 912 of theoptical material layer 906 to the lower surface 910 of the opticalmaterial layer 906 and the upper surface 902 of the substrate 900 in thefirst sections 922 of the optical material layer 906 exposed to theelectron beam through the apertures 918. Second sections 924 of theoptical material layer 906 was not exposed to the electron beam 920because the mask 914 absorbed or blocked the electron beam.

As shown in FIG. 14C, the aperture mask 914 is removed. The opticalmaterial layer 906 is removed from the substrate 900 by conventionalchemical, etching, physical means or the use of a release layer, asdiscussed previously.

After heating and electron beam irradiation through the mask aperture,the first section 922 of the optical material layer 906 will have anindex of refraction n₁, which is higher than the original index ofrefraction n₀ of the starting optical material layer, through the fullthickness 912 of the optical material layer. The second section 924 ofthe optical material layer 906, which was not exposed to the electronbeam irradiation, will have the original index of refraction n₀ of thestarting optical material layer. Since the starting optical materiallayer is one layer, after electron beam irradiation, the first sectionis integral and positioned adjacent to the second section within theoptical material layer.

The mask serves to restrict the electron beam spatially limiting itsirradiation to the apertured sections of the optical material layer.

The optical material layer will have adjacent sections of differentrefractive indexes but formed from the same optical material and can beused as a diffraction grating or interference filter.

The optical material layer will have adjacent sections of differentrefractive indexes without fabrication by deposition, without anintervening adhesive layer between the structure and layer or betweenadjacent sections, and with both adjacent sections being formed from thesame optical material.

The depth of the penetrating electron beam and the resulting thicknessof the altered refractive index layer are determined by the dose,voltage and duration of the electron beam and accordingly can vary fromthe upper surface of the starting optical material layer to the lowersurface of the microlens structure.

The electron beam can provide a uniform refractive index n₁ to theresulting irradiated optical material with adjacent sections ofdifferent refractive indexes, as discussed in FIG. 8, to form arefractive lens. Or the electron beam can provide a gradient refractiveindex n₂ to n₁ to the resulting irradiated optical material adjacentsections of different refractive indexes, as discussed in FIG. 11, toform a gradient index (GRIN) lens.

Multiple masking steps can provide multiple sections with multipledifferent refractive indexes in the same optical material layer formedfrom the same optical material. The multiple sectioned optical materiallayer with multiple different refractive indexes can be used as afresnel lens.

The electron beam can be incident at an angle to the aperture mask andthe surface of the starting optical material layer to form a tiltedrefractive index gradient.

As shown in the alternate embodiment of FIG. 15A, the starting opticalmaterial layer 1000 is positioned on the substrate layer 1002. Theelectron beam apparatus and method of FIG. 15 are the same as in FIG.14.

A mask 1004 with multiple apertures 1006 is positioned between theelectron beam source (not shown in this Figure) and the starting opticalmaterial layer 1000. The starting optical material layer 1006 will havean original index of refraction n₀ and a thickness 1008. The mask,starting optical material layer and substrate are all parallel.

A large area electron beam 1010 is incident at a 15 degree angle to themask 1004 and starting optical material 1000. The electron beamirradiates the exposed angled sections 1012 of the starting opticalmaterial layer through the apertures 1006 of the mask 1004. The electronbeam 1010 will be absorbed, or otherwise blocked, by the mask 1004 butwill be transmitted through the apertures 1006. Infrared radiation beams1014 will heat the substrate 1002 and, by heat transfer through thesubstrate, will heat the starting optical material 1000.

As shown in FIGS. 15A and 15B, the electron beam 1010 fully penetratesthe cross-sectional depth or thickness 1016 of the optical materiallayer 1000 to the lower surface 1018 of the optical material layer 1000and the upper surface 1020 of the substrate 1002 in the first exposedsections 1012 of the optical material layer 1000 through the apertures1006.

The exposed sections will have a varying gradient index of refractionfrom n₁ to n₂ by depth, with the upper refractive index n₂ closer to theupper surface 1022 being higher than the lower refractive index n₁closer to the lower surface 1018 through the full thickness 1008 of theoptical material layer 1000. Both refractive indexes n₁ to n₂ are higherthan the original index of refraction n₀ in the alternating section.

The second section 1024 of the optical material layer 100, which was notexposed to the electron beam irradiation due to the blocking orabsorbing by the mask 1004, will have the original index of refractionn₀ of the starting optical material layer.

As shown in FIG. 15B, the aperture mask 1004 is removed. The opticalmaterial layer 1000 is removed from the substrate 1002 by conventionalchemical, etching, physical means or the use of a release layer, asdiscussed previously.

The alternating first sections 1012 of high refractive index and thesecond sections 1024 of low refractive index are parallel to each otherbut are at a 15 degree angle to the upper surface 1022 and lower surface1018 of the optical material layer 1000 and will form a tiltedrefractive index gradient. Since the starting optical material layer isone layer, after electron beam irradiation, the first section isintegral and positioned adjacent to the second section within theoptical material layer.

The tilted index gradient can be used as an output coupling device, adiffraction grating or a beam-splitter. Light propagating within thealternating sections of low and varying high refractive index in theresulting optical material layer will be extracted by the tiltedgradient.

The mask serves to restrict the electron beam spatially limiting itsirradiation to the apertured sections of the optical material layer.

The depth of the penetrating electron beam and the resulting thicknessof the altered refractive index layer are determined by the dose,voltage and duration of the electron beam and accordingly can vary fromthe upper surface of the starting optical material layer to the lowersurface of the gradient index structure.

The electron beam can provide a uniform refractive index n₁ to theresulting irradiated optical material with adjacent sections ofdifferent refractive indexes, as discussed in FIG. 8, to form adiffraction grating or beam-splitter.

Multiple masking steps can provide multiple sections for the tiltedindex gradient with multiple different refractive indexes in the sameoptical material layer formed from the same optical material.

The electron beam with multiple masking steps can form a binarydiffractive optical element of the same optical material.

As shown in FIG. 16A, the substrate 1100 is a support ring with an uppersurface 1102 and a lower surface 1104. The starting optical materiallayer 1106 has an upper surface 1108 and a lower surface 1110.

A small portion 1112 of the lower surface 1110 of the starting opticalmaterial layer is deposited, bonded, coated, or otherwise positioned onthe upper surface 1102 of the substrate support ring. A large portion1114 of the lower surface 1110 of the starting optical material layerremains exposed.

The starting optical material layer 1106 will have an original index ofrefraction n₀ and a first or full thickness 1116.

As shown in FIG. 16B, a first aperture mask 1118 is positioned betweenthe electron beam source (not shown in this Figure) and the startingoptical material layer 1106. The first mask 1118 has an upper surface1120 and a single first aperture 1122.

A first large area electron beam 1124 is incident at a perpendicularangle to the upper surface 1108 of the optical material layer 1106through the first aperture 1122 of the first mask 1118 and irradiatesthe optical material layer through the first mask aperture 1122. Thefirst electron beam 1124 will be absorbed, or otherwise blocked, by thesurface 1120 of the first mask 1118 but will be transmitted through thefirst mask aperture 1122. First infrared radiation beams 1126 will heatthe exposed portion 1114 of the lower surface 1110 of the startingoptical material 1106.

As shown in FIG. 16C, the first electron beam 1124 fully penetrates thefirst depth or thickness 1126 of the optical material layer 1106 to thelower surface 1110 of the optical material layer 1106 in a first section1128 of the optical material layer 1106.

The remaining section 1130 of the optical material layer 1106 was notexposed to the electron beam 1124 because the mask 1118 absorbed orblocked the electron beam.

The first section 1128 of the optical material layer 1106 will have anindex of refraction n₁, which is higher than the original index ofrefraction n₀ of the starting optical material layer, through the fullfirst thickness 1116 of the optical material layer. The remainingsection 1130 of the optical material layer 1106, which was not exposedto the electron beam irradiation, will have the original index ofrefraction n₀ of the starting optical material layer.

The first aperture mask 1118 is removed.

As shown in FIG. 16D, a second aperture mask 1132 is positioned betweenthe electron beam source (not shown in this Figure) and the opticalmaterial layer 1106. The second mask 1132 has an upper surface 1134 anda single second aperture 1136. The second aperture 1136 in the secondaperture mask is wider than the first aperture 122 in the first aperturemask.

A second large area electron beam 1138 is incident at a perpendicularangle to the upper surface 1108 of the optical material layer 1106through the second aperture 1136 of the second mask 1132 and irradiatesthe optical material layer through the second mask aperture 1136. Thesecond electron beam 1138 will be absorbed, or otherwise blocked, by thesurface 1134 of the second mask 1132 but will be transmitted through thesecond mask aperture 1136. Second infrared radiation beams 1140 willheat the exposed portion 1114 of the lower surface 1110 of the startingoptical material 1106.

As shown in FIG. 16E, the second aperture mask 1132 is removed. Theoptical material layer 1106 is removed from the substrate 1100 byconventional chemical, etching, physical means or the use of a releaselayer, as discussed previously.

The second electron beam 1138 partially penetrates to a second depth orthickness 1142 of the optical material layer 1106 between the uppersurface 1108 and the lower surface 1110 of the optical material layer1106 in a second section 1144 of the optical material layer 1106. Theremaining section 1146 of the optical material layer 1106 was notexposed to the electron beam 1138 because the mask 1132 absorbed orblocked the electron beam.

The second section 1144 of the optical material layer 1106 will have anindex of refraction n₂, which is higher than the original index ofrefraction n₀ of the starting optical material layer. The remainingsection 1146 of the optical material layer 1106, which was not exposedto the electron beam irradiation, will have the original index ofrefraction n₀ of the starting optical material layer.

The second section 1144 of high refractive index is wider than the firstsection 1128 of high refractive index. The second section 1144 of highrefractive index has a shallower depth than the first section 1128 ofhigh refractive index. The second section 1144 of high refractive indexoverlaps in one area 1148 the first section 1128 of high refractiveindex. The overlap area 1148 will have an index of refraction n₃, whichis higher than the original index of refraction n₀ of the startingoptical material layer 1006.

The two beam exposure through two different size apertures forms abinary diffractive optical element 1150. The binary diffractive opticalelement 1150 is a two level diffractive element structure. The binarydiffractive optical element has a first level 1152 of the first section1128 of high refractive index and a second level 1154 of the secondsection 1144 of high refractive index including the overlap area 1148 ofhigh refractive index within the remaining section 1146 of lowrefractive index of the optical material layer 1106.

Multiple masks and multiple electron beam exposure of the startingoptical material will provide multiple refractive index sections for amultiple level diffractive structure for the binary diffractive opticalelement optical element. The binary or multiple level diffractiveoptical element can be used as a diffraction grating or a beam-splitter.

An aperture mask can be used with the electron beam apparatus and methodto provide a waveguide having a core of a high refractive indexsurrounded or partially surrounded by a cladding layer of a lowrefractive index of the same optical material.

As shown in FIG. 17A, the substrate 1200 has an upper surface 1202 and alower surface 1204. The starting optical material layer 1206 has anupper surface 1208 and a lower surface 1210. The lower surface 1210 ofthe starting optical material layer is deposited, bonded, coated, orotherwise positioned on the upper surface 1202 of the substrate. Thestarting optical material layer 1206 will have an original index ofrefraction n₀ and a thickness 1212.

As shown in FIG. 17B, an aperture mask 1214 is positioned between theelectron beam source (not shown in this Figure) and the starting opticalmaterial layer 1206. The mask 1214 has an upper surface 1216 andmultiple apertures 1218.

A large area electron beam 1220 is incident at a perpendicular angle tothe upper surface 1208 of the optical material layer 1206 through theapertures 1218 of the mask 1214 and irradiates the optical materiallayer through the mask apertures 1218. The electron beam 1220 will beabsorbed, or otherwise blocked, by the surface 1216 of the mask 1214 butwill be transmitted through the apertures 1218. Infrared radiation beams1222 will heat the substrate 1200 through the lower surface 1204 and, byheat transfer through the substrate, will heat the starting opticalmaterial 1206.

As shown in FIGS. 17B and 17C, the electron beam 1220 partiallypenetrates the depth or thickness 1212 of the optical material layer1206 to a depth or thickness 1224 between the upper surface 1208 and thelower surface 1210 of the optical material 1206 in the first sections1226 exposed to the electron beam through the aperture 1218. Anothersecond sections 1228 of the optical material layer 1206 were not exposedto the electron beam 1220 because the mask 1214 absorbed or blocked theelectron beam.

As shown in FIG. 17C, the aperture mask 1214 is removed. The opticalmaterial layer 1206 is removed from the substrate 1200 by conventionalchemical, etching, physical means or the use of a release layer, asdiscussed previously.

After heating and electron beam irradiation through the mask aperture,the first sections 1226 of the optical material layer 1206 will have anradial gradient index of refraction n₂ to n₁, which is higher than theoriginal index of refraction n₀ of the starting optical material layer,through the thickness 1224 of the optical material layer. The secondsections 1228 of the optical material layer 1206, which were not exposedto the electron beam irradiation, will have the original index ofrefraction n₀ of the starting optical material layer. Since the startingoptical material layer is one layer, after electron beam irradiation,the first sections are integral and positioned adjacent to the secondsections within the optical material layer.

The first sections 1226 of high refractive index form a waveguide corelayer in the surrounding second sections 1228 of low refractive indexstarting optical material layer which functions as a waveguide claddinglayer. The waveguide 1230 extends from the surface 1208 of the opticalmaterial layer 1206 with its core layer 1226 partially surrounded by thecladding layer 1228.

As shown in FIG. 17D, a second layer 1232 of starting optical materialcan be deposited, bonded, coated, or otherwise positioned on the uppersurface 1208 on the core layer 1226 and the first starting opticalmaterial 1206 to completely surround the high refractive index corelayer with a low refractive index cladding layer to form the waveguide1234.

The temperature of the substrate supporting the starting opticalmaterial, the voltage of the electron beam, the dose of the electronbeam, the duration and number of steps of the electron beam, the use ofoxidizing or non-oxidizing gases in the low vacuum atmosphere, can eachseparately, or in combination, be varied to fabricate a uniform index ofrefraction for the core layer of the waveguide.

As shown in FIG. 18A, the substrate 1300 has an upper surface 1302 and alower surface 1304. The starting optical material layer 1306 has astepped pattern upper surface with alternating high upper surfaces 1308and low upper surfaces 1310 across the width of the starting opticalmaterial layer. The flat surfaces 1308 and 1310 are offset from eachother by a first depth 1312. The starting optical material layer 1306has a flat lower surface 1314. The lower surface 1314 of the startingoptical material layer is deposited, bonded, coated, or otherwisepositioned on the upper surface 1302 of the substrate. The startingoptical material layer 1306 will have an original index of refraction n₀and a thickness 1316.

As shown in FIG. 18B, a first large area electron beam 1318 is incidentat a perpendicular angle to the upper surfaces 1308 and 1310 of theoptical material layer 1306 and irradiates the optical material layer.Infrared radiation beams 1320 will heat the substrate 1300 through thelower surface 1304 and, by heat transfer through the substrate, willheat the starting optical material 1306.

The electron beam 1318 partially penetrates the optical material layerto a second depth or thickness 1322 from the upper surfaces 1308 and1310 into the optical material layer 1306. The penetration depth 1322 isless than the thickness 1316 of the optical material layer.

As shown in FIG. 18C, the optical material layer 1306 is removed fromthe substrate 1300 by conventional chemical, etching, physical means orthe use of a release layer, as discussed previously.

The electron beam irradiation and heating forms first sections 1324 ofrefractive index change extending from the high upper surfaces 1308 intothe optical material layer 1306 to a depth 1322 and second sections 1326of refractive index change extending from the low upper surfaces 1310into the optical material layer 1306 to a depth 1322. The first sections1324 and second sections 1326 are identical except for the relativedifference in first depth 1312 into the optical material 1306. The firstand second sections 1324 and 1326 of refractive index change each havean index of refraction have an radial gradient index of refraction n₂ ton₁, which is higher than the original index of refraction n₀ of thestarting optical material layer, through the thickness 1322 of theoptical material layer 1306.

A third section 1328 of the optical material layer 1306 which were notexposed to the electron beam irradiation, will have the original indexof refraction n₀ of the starting optical material layer.

Since the starting optical material layer is one layer, after electronbeam irradiation, the first section is integral and positioned adjacentto the third section within the optical material layer and the secondsection is integral and positioned adjacent to the third section withinthe optical material layer.

The first sections 1324 of high refractive index form a waveguide corelayer in the surrounding third section 1328 of low refractive indexstarting optical material layer which functions as a waveguide claddinglayer. The waveguide 1330 extends from the surface 1308 of the opticalmaterial layer 1306 with its core layer 1324 partially surrounded by thecladding layer 1328.

The second sections 1326 of high refractive index form a waveguide corelayer in the surrounding third section 1328 of low refractive indexstarting optical material layer which functions as a waveguide claddinglayer. The waveguide 1330 extends from the surface 1308 of the opticalmaterial layer 1306 with its core layer 1326 partially surrounded by thecladding layer 1328.

As shown in FIG. 18D, a second layer 1332 of starting optical materialcan be deposited, bonded, coated, or otherwise positioned on the uppersurface 1308 on the core layers 1324 and 1326 and the first startingoptical material 1306 to completely surround the high refractive indexcore layer with a low refractive index cladding layer to form thewaveguides 1334.

The variable depths of the upper surface allow for precise positioningof the core layer of the waveguide in the cladding layer. The variablespacing between the waveguides allows for precise positioning relativeto each other.

The temperature of the substrate supporting the starting opticalmaterial, the voltage of the electron beam, the dose of the electronbeam, the duration and number of steps of the electron beam, the use ofoxidizing or non-oxidizing gases in the low vacuum atmosphere, can eachseparately, or in combination, be varied to fabricate a uniform index ofrefraction for the core layer of the waveguide.

As shown in FIG. 19A, the substrate 1400 is a support ring with an uppersurface 1402 and a lower surface 1404. A first optical material layer1406 has an upper blazed surface 1408 and a lower surface 1410. A smallportion 1412 of the lower surface 1410 of the starting optical materiallayer is deposited, bonded, coated, or otherwise positioned on the uppersurface 1402 of the substrate support ring. A large portion 1414 of thelower surface 1410 of the starting optical material layer remainsexposed.

A second optical material layer 1416 has a blazed upper surface 1418 anda blazed lower surface 1420. A third optical material layer 1422 has anupper surface 1424 and a blazed lower surface 1426.

The lower blazed surface 1420 of the second optical material layer 1416is deposited, bonded, coated, or otherwise positioned on the upperblazed surface 1408 of the first optical material layer 1406. The lowerblazed surface 1426 of the third optical material layer 1422 isdeposited, bonded or otherwise positioned on the upper blazed surface1418 of the second optical material layer 1416. The second opticalmaterial layer 1406 will have an original index of refraction n₀. Thefirst and third optical material layers will be formed of differentmaterial than the second optical material layer but will also have anindex of refraction of n₀.

As shown in FIG. 19B, an aperture mask 1428 is positioned between theelectron beam source (not shown in this Figure) and the third opticalmaterial layer 1422. The mask 1428 has an upper surface 1430 and asingle aperture 1432.

A large area electron beam 1434 is incident at a perpendicular angle tothe upper surface 1424 of the third optical material layer 1422 throughthe aperture 1432 of the mask 1428 and irradiates the third opticalmaterial layer 1422 and the underlying second optical material layer1416 through the mask aperture 1432. The electron beam 1434 will beabsorbed, or otherwise blocked, by the surface 1430 of the mask 1428 butwill be transmitted through the aperture 1432. Infrared radiation beams1436 will heat the first optical material layer 1406 through the exposedportion 1414 of the lower surface 1410 and, by heat transfer through thefirst optical material layer 1406, will heat the second optical materiallayer 1416.

The electron beam 1434 fully penetrates the third optical material layer1422 and fully penetrates the second optical material layer 1416 to theupper surface 1408 of the first optical material layer 1406 in the firstsection 1438 of the second optical material layer 1426 exposed to theelectron beam through the aperture 1432. A second section 1440 of thesecond optical material layer 1416 was not exposed to the electron beam1434 because the mask 1428 absorbed or blocked the electron beam. Theelectron beam irradiation will not effect the third optical materiallayer 1422. The electron beam irradiation will effect the second opticalmaterial layer 1416, which is formed of a different optical materialthan the third and first optical material layers.

As shown in FIG. 19C, the substrate 1400 is removed from the firstoptical material layer 1406 by conventional chemical, etching, physicalmeans or the use of a release layer, as discussed previously.

After heating and electron beam irradiation through the mask aperture,the first section 1438 of the second optical material layer 1416 willhave a radial gradient index of refraction n₂ to n₁, which is higherthan the original index of refraction n₀ of the second optical materiallayer 1416 and higher than the index of refraction n₀ of the first andthird optical material layers 1406 and 1422, through the thickness 1442of the second optical material layer 1416. The second section 1440 ofthe second optical material layer 1406, which was not exposed to theelectron beam irradiation, will have the original index of refraction n₀of the second optical material layer 1416.

The first section 1438 of high refractive index forms a waveguide corelayer in the surrounding second optical material layer 1416, firstoptical material layer 1406 and third optical material layer 1422 of lowrefractive index which function as a waveguide cladding layer.

The waveguide 1444 extends from the upper surface grating 1446 from theupper blazed surface 1418 to the lower surface grating 1448 from thelower blazed surface 1420 with its core layer 1438 partially surroundedby the cladding layers 1416, 1406, and 1422.

The temperature of the substrates supporting the starting opticalmaterial, the voltage of the electron beam, the dose of the electronbeam, the duration and number of steps of the electron beam, the use ofoxidizing or non-oxidizing gases in the low vacuum atmosphere, can eachseparately, or in combination, be varied to fabricate a uniform index ofrefraction for the core layer of the waveguide.

As shown in FIG. 20A, the substrate 1500 is a support ring with an uppersurface 1502 and a lower surface 1504. The starting optical materiallayer 1506 has an upper surface 1508 and a lower surface 1510. A smallportion 1512 of the lower surface 1510 of the starting optical materiallayer 1506 is deposited, bonded, coated, or otherwise positioned on theupper surface 1502 of the substrate support ring 1500. A large portion1514 of the lower surface 1510 of the starting optical material layer1506 remains exposed. The starting optical material layer 1506 will havean original index of refraction n₀ and a thickness 1516.

As shown in FIG. 20B, a first embossed wax structure 1518 has a concavecurved upper surface 1520 and a flat lower surface 1522. The lowersurface 1522 of the first embossed structure 1518 is deposited on theupper surface 1508 of the starting optical material layer 1506. A secondembossed wax structure 1524 has a concave curved lower surface 1526 anda flat upper surface 1528. The upper surface 1528 of the second embossedstructure 1524 is deposited on the lower surface 1510 of the startingoptical material layer 1506. The first and second embossed waxstructures are identical in shape and aligned in mirror image fashion onopposite surfaces of the starting optical material layer.

A first large area electron beam 1530 is incident at a perpendicularangle to the upper surface 1520 of the first embossed structure 1518 andirradiates the first embossed structure 1518 and the starting opticalmaterial layer 1506. Infrared radiation beams 1532 will heat thestarting optical material 1506 from an angle to the lower surface 1510of the starting optical material layer 1506.

The first electron beam 1530 fully penetrates the first embossedstructure 1518 and partially penetrates the starting optical materiallayer 1506 through its upper surface 1508 between the upper surface 1508and the lower surface 1510 of the optical material layer.

A second large area electron beam 1534 is incident at a perpendicularangle to the lower surface 1526 of the second embossed structure 1524and irradiates the second embossed structure 1524 and the startingoptical material layer 1506. Infrared radiation beams 1536 will heat thestarting optical material 1506 from an angle to the upper surface 1508of the starting optical material layer 1506.

The second electron beam 1534 fully penetrates the second embossedstructure 1524 and partially penetrates the starting optical materiallayer 1506 through its lower surface 1510 between the lower surface 1510and the upper surface 1508 of the optical material layer.

The first electron beam and the second electron beam can irradiate thestarting optical material layer simultaneously.

As shown in FIG. 20C, the first embossing structure 1518 and the secondembossing structure 1524 are removed from the optical material layer1506 by conventional means. The substrate 1500 is removed from the firstoptical material layer 1506 by conventional chemical, etching, physicalmeans or the use of a release layer, as discussed previously.

The partial penetration of the first electron beam will form a firstsection 1538 in the optical material layer 1506 having a radial gradientindex of refraction n₂ to n₁, which is higher than the original index ofrefraction n₀ of the optical material layer. The first section 1538extends from the upper surface 1508 into the optical material layer 1506past the midpoint 1540 of depth 1516 towards the lower surface 1510 in asemi-curved area 1542. The semi-curved area is in proportion to theelectron beam irradiation through the curved surface of the embossedstructure.

The partial penetration of the second electron beam will form a secondsection 1544 in the optical material layer 1506 having a radial gradientindex of refraction n₂ to n₁, which is higher than the original index ofrefraction n₀ of the optical material layer. The first section extendsfrom the lower surface 1510 into the optical material layer 1506 pastthe midpoint 1540 of depth 1516 towards the upper surface in asemi-curved area 1546. The semi-curved area is in proportion to theelectron beam irradiation through the curved surface of the embossedstructure.

A third section 1548 of the surrounding optical material layer 1506,which was not exposed to the electron beam irradiation, will have theoriginal index of refraction n₀ of the starting optical material layer.

The first high refractive index section 1538 and second high refractiveindex section 1544 will overlap in an overlapping section 1550 in theoptical material layer 1506. The overlap section 1550 will be exposed toirradiation from both the first and second electron beams. The overlapsection will have a radial gradient index of refraction n₄ to n₃, whichis higher than the radial gradient index of refraction n₂ to n₁ of thefirst and second sections 1538 and 1544 and higher than the originalindex of refraction n₀ of the optical material layer.

The high refractive index overlap section 1550 forms a waveguide corelayer with the first section 1538, second section 1544 and third section1548 of lower refractive indexes being the cladding layer of thewaveguide surrounding the core layer.

The waveguide 1552 extends through the midpoint 1540 of the opticalmaterial layer 1506 completely surrounded by cladding layers 1538, 1544and 1548.

Since the starting optical material layer is one layer, after electronbeam irradiation, the first section is integral and positioned adjacentto the third section within the optical material layer, the secondsection is integral and positioned adjacent to the third section and theoverlapping section is integral and positioned adjacent to the firstsection, second section and third section within the optical materiallayer.

Alternately, only one heating source will heat the starting opticalmaterial layer with infrared radiation beams 1532 from below thestarting optical material layer or infrared radiation beams 1536 fromabove the starting optical material layer.

Also alternately, the formation of the waveguide can be a two stepprocess with the first step being positioning the first embossingstructure and the first electron beam irradiation from above the opticalmaterial layer and the second step of the positioning of the secondembossing structure and the second electron beam irradiation from belowthe optical material layer.

As shown in FIG. 20D, the first and second wax structures (not shown inthis Figure) can be slightly out of alignment. The first section 1554 ofhigh refractive index will form a first waveguide core layer on theupper surface 1508 with the partially surrounding starting opticalmaterial layer 1506 being the cladding layer of the first waveguide. Thesecond section 1556 of high refractive index will form a secondwaveguide core layer on the lower surface 1510 with the partiallysurrounding starting optical material layer 1506 being the claddinglayer of the second waveguide. In this instance, the first section 1554of high refractive index and the second section 1556 of high refractiveindex do not overlap in the optical material layer 1506.

The embossed structures can be varied in the shape of the surfaces. Thewaveguides formed by the embossed structures cane be overlapping orisolated depending upon the alignment or nonalignment of the embossedstructures on opposite surfaces of the optical material layer.

The temperature of the substrates supporting the starting opticalmaterial, the voltage of the electron beam, the dose of the electronbeam, the duration and number of steps of the electron beam, the use ofoxidizing or non-oxidizing gases in the low vacuum atmosphere, can eachseparately, or in combination, be varied to fabricate a uniform index ofrefraction for the core layer of the waveguide.

The use of masks in the electron beam apparatus and method allows thefabrication of optical interconnects in complex three dimensionaloptical elements by providing narrow waveguides and waveguides that canalign between layers as shown in FIG. 21.

As shown in FIG. 21, a first waveguide 1600 in the upper layer 1602 ispatterned to divide into a first branch waveguide 1604 and a secondbranch waveguide 1606. The first branch waveguide 1604 continues on inthe upper layer 1602. The second branch waveguide 1606 interconnects ina mating pattern to a second waveguide 1608 in the lower layer 1610.

A laser diode 1612 is mounted such that an emitted light beam 1614 iscoupled into the upper top layer 1602 while the lower bottom layer 1610acts as a spacer to physically set the upper top layer 1602 at theappropriate height from a substrate 1616. The light beam 1614 emitted bythe laser diode 1612 couples into the first waveguide 1610 as isillustrated by the dashed lines in the top layer. Halfway through theupper layer 1602, the first waveguide 1610 splits into two branches 1604and 1606. A first branch waveguide 1604 continues to guide the lightbeam 164 within the upper top layer 1602. A second branch waveguide 1606continues to guide the light beam 1614 and transitions into the lowerbottom layer 1610 and a second waveguide 1608. This transition can becreated by varying the penetration depth.

These optical material layers can be used as overlays on activecomponents such as microprocessors, Vertical Cavity Simulated EmissionLasers (VCSELs), laser diodes, and Micro-Electro-Mechanical Systems(MEMS) devices. Lift off techniques using soluble or meltable temporaryattachment means are also embodied in this invention. A lifted offoptical material layers or a supported optical material layers can beattached to non-flat substrates and incorporated into or on a printedcircuit board. These optical material layers can be combined withoptical components such as prisms, gratings, waveplates and opticalamplifiers.

The electron beam apparatus and method can form an optical fiber for useas a waveguide having a core of a high refractive index surrounded by acladding layer of a low refractive index formed of the same opticalmaterial.

As shown in FIG. 22A, a cylindrical strand 1700 of starting opticalmaterial has an outer surface 1702 and a center 1704. The startingoptical material strand 1700 will have an original index of refractionn₀ and a diameter 1706. The strand is supported and mounted between afirst roller 1708 and a second roller 1710. The first and second rollers1708 and 1710 rotate in the same direction, driven by a conventionalmotor (not shown in this Figure), as is known in the art. The strand1700 rotates along its length as the rollers rotate.

As shown in FIG. 22B, a large area electron beam 1712 is incident at aperpendicular angle to the outer surface 1702 of the optical materialstrand 1700 and irradiates the optical material strand. Infraredradiation beams 1714 will heat the starting optical material 1700through the outer surface 1702 on the side of the strand away from theelectron beam irradiation. The strand rotates during electron beamirradiation and heating.

The electron beam 1712 partially penetrates optical material strand 1700to a depth or thickness 1716 through the outer surface 1702 past thecenter 1704 of the strand.

As shown in FIG. 22C, the electron beam 1712 irradiates the cylindricalstrand 1700 of optical material unevenly across its diameter 1706. Thefirst electron beam irradiation area 1718 at 0 degrees of rotationextends past the center 1704 of the strand 1700. The second electronbeam irradiation area 1720 at 120 degrees of rotation extends past thecenter 1704 of the strand 1700. The third electron beam irradiation area1722 at 240 degrees of rotation extends past the center 1704 of thestrand 1700.

An inner cylindrical section 1724 of the cylindrical strand 1700 havinga diameter 1726 around the center 1704 receives constant overlappingelectron beam irradiation during rotation of the strand. An outersection 1728 near the outer surface 1702 of the cylindrical strandbetween the diameter 1726 of the inner cylindrical section and diameter1706 of the cylindrical strand receives intermittent electron beamirradiation during an angular range of degrees of rotation. The electronbeam will irradiate the cylindrical strand though a full 360 degrees ofrotation. The areas at 0 degrees, 120 degrees and 240 degrees are merelyillustrative examples.

As shown in FIG. 22D, after heating and electron beam irradiation, theouter section 1728 near the outer surface 1702 of the cylindrical strand1700 will have a radial gradient index of refraction n₂ to n₁ fromdiameter 1726 to the outer surface 1702 which is higher than theoriginal index of refraction n₀ of the starting optical material.

The inner cylindrical section 1724 of the cylindrical strand 1700 willhave a radial gradient index of refraction n₄ to n₃ from center 1704 todiameter 1726 which is higher than the original index of refraction n₀of the starting optical material layer and which is higher than thegradient index of refraction n₂ to n₁ of the outer section.

Since the starting optical material strand is one strand, after electronbeam irradiation, the inner section is integral and positioned adjacentto the outer section within the optical material.

The inner section 1724 of the cylindrical strand 1700 forms the highrefractive index core layer of a waveguide 1730. The outer section 1728of the cylindrical strand 1700 forms the low refractive index claddinglayer of a waveguide 1730. The cladding layer surrounding the core layerforms a waveguiding optical fiber 1730 of the same optical material.

To provide uniform exposure of the cylindrical optical material 1700along its cross-sectional diameter, the strand 1700 may rotate under theelectron beam 1712 as seen in FIG. 22B or the electron beam 1712 mayrotate around the strand 1700 (not shown in this Figure) or both thestrand 1700 and electron beam 1712 may rotate in opposite directions orat differing speeds in the same direction (not shown in this Figure).

The temperature of the substrate supporting the starting opticalmaterial, the voltage of the electron beam, the dose of the electronbeam, the duration and number of steps of the electron beam, the use ofoxidizing or non-oxidizing gases in the low vacuum atmosphere, can eachseparately, or in combination, be varied to fabricate a uniform index ofrefraction for the cladding layer or the core layer of the opticalfiber.

While there has been described herein the principles of the invention,it is to be clearly understood to those skilled in the art that thisdescription is made only by way of example and not as a limitation tothe scope of the invention. Accordingly, it is intended, by the appendedclaims, to cover all modifications of the invention which fall withinthe true spirit and scope of the invention.

1. A method for forming an optical element comprising the steps of:positioning an optical material in a near vacuum, said optical materialhaving a first index of refraction; exposing said optical material witha large area electron beam; and controlling the energy of the electronbeam to raise the index of refraction of a first portion of said opticalmaterial to a second index of refraction, said second index ofrefraction higher than said first index of refraction, to form anoptical element from said first portion of said optical material with ahigher second index of refraction and the remaining second portion ofsaid optical material with the first index of refraction.
 2. The methodfor forming an optical element of claim 1 further comprising the step ofmaintaining a constant temperature of said optical material.
 3. Themethod for forming an optical element of claim 1 comprising the step ofpositioning at least one mask with at least one aperture in the path ofsaid electron beam such that said mask blocks said electron beam andsaid aperture transmits said electron beam to raise the refractive indexof said first portion of said optical material.
 4. The method forforming an optical element of claim 1 comprising the step of applyingsaid optical material to a support member, said applying comprisescasting, spin coating, dip coating, chemical vapor deposition,embossing, spraying, roller coating, meniscus coating, or extrusion. 5.The method for forming an optical element of claim 1 wherein controllingthe energy of the electron beam to raise the index of refraction of afirst portion of said optical material to a second gradient index ofrefraction, said second gradient index of refraction higher than saidfirst index of refraction, to form an optical element from said firstportion of said optical material with a higher second gradient index ofrefraction and the remaining second portion of said optical materialwith the first index of refraction.
 6. The method for forming an opticalelement of claim 1 wherein controlling the energy of the electron beamto raise the index of refraction of a first portion of said opticalmaterial to a second uniform index of refraction, said second uniformindex of refraction higher than said first index of refraction, to forman optical element from said first portion of said optical material witha higher second uniform index of refraction and the remaining secondportion of said optical material with the first index of refraction. 7.A method for forming an optical element comprising the steps of:positioning an optical material layer in a near vacuum, said opticalmaterial layer having a first index of refraction; exposing said opticalmaterial layer with a large area electron beam; and controlling theenergy of the electron beam to raise the index of refraction of a firstsub-layer of said optical material to a second index of refraction, saidsecond index of refraction higher than said first index of refraction,to form an optical element from said first sub-layer of said opticalmaterial with a higher second index of refraction and the remainingsecond sub-layer of said optical material with the first index ofrefraction.
 8. The method for forming an optical element of claim 7wherein said large are electron beam partially penetrates said opticalmaterial layer to form said first sub-layer of a higher second index ofrefraction.
 9. The method for forming an optical element of claim 7further comprising the step of: inverting said optical element to forman interference filter.
 10. The method for forming an optical element ofclaim 9 wherein said interference filter is an anti-reflection coatingfor an optical element.
 11. The method for forming an optical element ofclaim 9 wherein said interference filter is a heat reflective thermalcontrol layer for an optical element.
 12. The method for forming anoptical element of claim 9 wherein said interference filter is awavelength sensitive reflectance/transmittance interference filter foran optical element.
 13. The method for forming an optical element ofclaim 9 wherein said interference filter is a diffraction grating. 14.The method for forming an optical element of claim 9 wherein saidinterference filter is a beam-splitter.
 15. A method for forming abinary diffractive optical element comprising the steps of: positioningan optical material layer in a near vacuum, said optical material layerhaving a first index of refraction; exposing said optical material layerwith a large area electron beam; and controlling the energy of theelectron beam to alter the index of refraction of multiple sub-layers ofsaid optical material layer to form a multiple level diffractivestructure within said optical material layer.
 16. The method for forminga binary diffractive optical element of claim 15 comprising the step of:sequentially positioning multiple masks, each of said multiple maskswith at least one aperture, in the path of said electron beam such thateach of said multiple masks blocks said electron beam and each of saidapertures transmits said electron beam to raise the refractive index ofsaid multiple sub-layers of said optical material.
 17. A method forforming an optical element comprising the steps of: positioning anoptical material in a near vacuum, said optical material having a firstindex of refraction; exposing said optical material with a large areaelectron beam; and controlling the energy of the electron beam to raisethe index of refraction of at least one first area of said opticalmaterial to a second index of refraction, said second index ofrefraction higher than said first index of refraction, to form anoptical element from said at least one first area of said opticalmaterial with a higher second index of refraction and the remaining atleast one second area of said optical material with the first index ofrefraction.
 18. The method for forming an optical element of claim 17wherein said at least one first area is a microlens.
 19. The method forforming an optical element of claim 17 wherein multiple first areasalternate with multiple second areas to form a diffraction grating. 20.The method for forming an optical element of claim 17 wherein multiplefirst areas alternate with multiple second areas to form abeam-splitter.
 21. The method for forming an optical element of claim 17wherein said optical element is a waveguide with said at least one firstarea forms the core layer of said waveguide and said at least one secondarea forms the cladding layer of said waveguide.
 22. A method forforming an optical element comprising the steps of: positioning anoptical material layer in a near vacuum, said optical material layerhaving a first index of refraction; positioning an embossed structure onsaid optical material layer; exposing said optical material layerthrough said embossed structure with a large area electron beam; andcontrolling the energy of the electron beam to raise the index ofrefraction of a first area of said optical material to a second index ofrefraction, said second index of refraction higher than said first indexof refraction, to form an optical element from said first area of saidoptical material with a higher second index of refraction and theremaining second area of said optical material with the first index ofrefraction.
 23. The method for forming an optical element of claim 22further comprising the step of maintaining a constant temperature ofsaid optical material layer.
 24. The method for forming an opticalelement of claim 22 wherein said optical element is a waveguide withsaid first area forms the core layer of said waveguide and said secondarea forms the cladding layer of said waveguide.
 25. A method forforming a waveguide comprising the steps of: positioning an opticalmaterial layer in a near vacuum, said optical material layer having afirst index of refraction, said optical material layer having a firstsurface and a second surface, said second surface being opposite saidfirst surface; positioning a first embossed structure on said firstsurface of said optical material layer; positioning a second embossedstructure on said second surface of said optical material layer;exposing said optical material layer through said first embossedstructure with a first large area electron beam; exposing said opticalmaterial layer through said second embossed structure with a secondlarge area electron beam; controlling the energy of said first electronbeam to raise the index of refraction of a first area of said opticalmaterial to a second index of refraction, said second index ofrefraction higher than said first index of refraction; and controllingthe energy of said second electron beam to raise the index of refractionof a second area of said optical material to a third index ofrefraction, said third index of refraction higher than said first indexof refraction, said first area and said second area overlapping in saidoptical material layer to form a core layer for said waveguide, saidfirst area and said second area and said optical material layer forminga cladding layer for said waveguide, said cladding layer surroundingsaid core layer.
 26. The method for forming a waveguide of claim 25further comprising the step of maintaining a constant temperature ofsaid optical material layer.
 27. The method for forming a waveguide ofclaim 25 wherein said positioning a second embossed structure on saidsecond surface of said optical material layer and said exposing saidoptical material layer through said second embossed structure with asecond large area electron beam occur after said positioning a firstembossed structure on said first surface of said optical material layerand said exposing said optical material layer through said firstembossed structure with a first large area electron beam.
 28. A methodfor forming an optical fiber comprising the steps of: positioning acylindrical strand of optical material having a first index ofrefraction in a near vacuum; exposing said cylindrical strand of opticalmaterial with a large area electron beam; controlling the energy of theelectron beam to raise the index of refraction of a first cladding layerto a second index of refraction, said second index of refraction higherthan said first index of refraction; and controlling the energy of theelectron beam to raise the index of refraction of a second core layer toa third index of refraction, said third index of refraction higher thansaid first index of refraction, said third index of refraction higherthan said second index of refraction, said first cladding layersurrounding said second core layer, said core layer and said claddinglayer forming a waveguide.
 29. The method for forming an optical fiberof claim 28 further comprising the step of: rotating said cylindricalstrand of optical material during said exposing said cylindrical strandof optical material with a large area electron beam.
 30. The method forforming an optical fiber of claim 28 further comprising the step ofmaintaining a constant temperature of said cylindrical strand of opticalmaterial.